As hitherto known, formation of a low-density foam product or low-density polyurethane foam to produce a certain article adapted for use in an automobile has been effected, using a combination of water and chlorofluorocabons as an effervescing agent during the foaming steps. But, such foaming process employing the combination of water and chlorofluorocarbons as an effervescing agent will result in destruction of the ozonosphere, which raises an environmental problem.
Therefore, avoiding use of chlorofulorocarbons is required. An example of technical solution thereto is taught in the Laid-Open Patent Publication No. Hei 11-293027 which describes a process for forming a polyurethane foam integrally together with a surface cover element, without use of chlorofluorocarbons, to produce a foam product integral with surface cover element, such as a headrest or an armrest.
Devices used in this prior-art process include the following three storage containers: a first storage container in which a first liquid material required for production of a given polyurethane resin is stored, the first liquid material containing a polyisocyanate as a primary ingredient; a second storage container in which a second liquid material required for production of the aforesaid polyurethane resin is stored, the second liquid material containing a polyol as a primary ingredient; and a third storage container in which stored is an additional liquid material containing a polyol as a primary ingredient, an organometallic catalyst, an effervescing agent and other required additives, such that a percentage of content of all those ingredients and additives is made equal to a percentage of content of the second liquid material (without addition of tertiary amine catalyst therein), wherein a supply tube is provided for flow communication with the third storage container to permit supply of those ingredients and additives into that container. Further, this third storage container is equipped with a CO2 gas loading device, so that the aforesaid ingredients and additives stored in the third storage container may be mixed with carbon oxide to the extent that the carbon oxide becomes saturated therein.
The first, second and third liquid materials respectively stored in the first, second and third storage containers are supplied at their respective predetermined ratio of flow and via their respective supply tubes into a mixing chamber called “mixing head”, after which, all those three liquid materials are jet discharged by a force of high pressure into the mixing chamber and are subjected to instantaneous stirring and mixing with one another. Then, the mixture is discharged from a discharge opening formed in an end of that mixing head to the outside (e.g. to an inside of a molding or die). After then, the three liquid materials in the discharged mixture start to react on each other for polymerization (i.e. polymerizing reaction), while being foamed. Accordingly, a desired shape of polyurethane foam can be obtained from the thus-mixed materials.